for those of you who use Gimp I created this fu-script for creating the backgrounds for elemental logos.
to use it drop it in your \Gimpxx\Script folder and do Filters->FU-Script->Refresh Scripts from inside gimp.
Now go to file->Create->Elemental->Elemental Logo
You can play with the type of background e.g. solid, Horizontal or vertical halves or quarters, set two base colors to use and determine how mottled the background is (this option gives it a more water color effect.
When it's exicuted you will see a black square this is the top layer for you to paint the foreground image on, look in layers to turn it off and show the generated background.
I'm assuming familiarity with how to create a mask and merge down layers once you have painted the foreground image.
Have a play and tell me what you think